Jeffrey A. Melby

Wave Overtopping of Levees and Overwash of Dunes

Abstract Earthen levees are designed for little wave overtopping during a design storm, but excessive overtopping and overflow can occur due to the combined effects of an extreme storm, sea level rise, and land subsidence. The transition from little wave overtopping to excessive wave overtopping and overflow on an impermeable smooth levee is examined in wave-flume experiments consisting of 107 tests. Existing empirical formulas are shown to be applicable to the cases of excessive wave overtopping and overflow in these tests. A numerical model based on time-averaged continuity, momentum, and wave action equations is connected to a new probabilistic model for the wet-and-dry zone, in order to predict the cross-shore variations of the mean and standard deviation of the free surface elevation and depth-averaged fluid velocity from outside the surf zone to the inner slope of the levee. The new model is calibrated to predict the measured overtopping and overflow rates within a factor of about two. The agreement is also shown to be similar for the water depths and velocities measured in the wet-and-dry zone on six different structures in 100 Dutch tests. The developed hydrodynamic model is coupled with new formulas for suspended-sand and bedload transport rates to predict dune erosion and overwash. The coupled model is compared with two small-scale tests on dune erosion with minor overwash, three large-scale tests on dune erosion, and field data on dune erosion and overwash due to severe storms lasting several days. The overwashed-dune profiles are predicted reasonably well, but the coupled model will need to be evaluated using measurements of wave overtopping and overwash rates.

Wave runup, transmission, and reflection for structures armored with CORE-LOC®

Wave-induced runup and wave transmission due to overtopping are important variables in coastal structure design. Many studies have been performed on different types of armor layers, but there is no generalized design guidance available on CORE-LOC® armor layer performance with respect to wave runup and transmission. An experimental study was performed to investigate the runup and transmission response of a CORE-LOC® armor layer. Wave runup and transmitted wave heights were measured for a wide range of wave, water level, and structure conditions in order to develop predictive tools for CORE-LOC® layer response. A new empirical model to predict runup levels was developed based on an existing model for rock revetments. Further, an analysis of transmission data was conducted to give insight and guidance for design purposes. Reflection coefficients were also analyzed.

Wave Overtopping and Damage Progression of Stone Armor Layer

A probabilistic hydrodynamic model for the wet and dry zone on a permeable structure is developed to predict irregular wave action on the structure above the still water level. The model is based on the time-averaged continuity and momentum equations for nonlinear shallow-water waves coupled with the exponential probability distribution of the water depth. The model predicts the cross-shore variations of the mean and standard deviation of the water depth and horizontal velocity. The model is compared with four test series in which measurement was made of the wave overtopping rate and probability as well as the water depth, velocity, and discharge exceeded by 2% of incident 1,000 waves. The agreement is mostly within a factor of 2. Damage progression of a stone armor layer is predicted by modifying a formula for bed load on beaches with input from the hydrodynamic model. The damage progression model is compared with three tests that lasted up to 28.5 h. The model predicts the eroded area of the damaged armor layer well but overpredicts the deposited area because it does not account for discrete stone units deposited at a distance seaward of the toe of the damaged armor layer.

Stone Armor Damage Initiation and Progression Based on the Maximum Wave Momentum Flux

Abstract The armor layer on the sea side of a rubble structure must be designed to protect against incident waves during storms. Formulas for armor stability and damage progression have been developed and are widely used for practical applications. However, none of the formulas accounts for the water depth at the toe of the structure explicitly. An alternative approach based on the maximum wave momentum flux at the toe of the structure is proposed in this article. Equations for sizing stable armor stone for constant incident waves and water level are proposed and calibrated using available data. Equations are also developed for determining damage progression in a life-cycle analysis involving varying wave and water level characteristics. The developed equations are calibrated using the damage progression tests conducted previously by the authors and verified using an additional 10 tests conducted for this article.

Dynamic response of dolos armor units

Abstract Concrete armor units are commonly employed for the protection of shorelines and rubble structures. Their design is primarily based on hydrodynamic stability, but their structural response to wave loading is poorly understood. In this study a wave force model is presented, which includes drag, inertia, kinetic and buoyant force components, to estimate hydrodynamic loads on the concrete armor unit, dolos. These loads are employed in a three-dimensional FEM analysis to determine the dynamic states of stress in a 42-ton dolos.

STRUCTURAL RESPONSE OF DOLOS IN WAVES

The Labrador Sea Extreme Waves Experiment (LEWEX), is an international basic research programme concerned with full-scale measurements, analysis, modelling and simulation in test basins of 3-dimensional seas. The research is carried out in order to assess the significance of 3-dimensional sea states in engineering applications. The first phase of the programme full scale wave measurements in the North Atlantic Ocean was performed at a site and time that had a high probability of encountering severe sea states. The present publication shows examples of measured bi-modal directional sea spectra obtained with the WAVESCAN buoy and directional sea spectra measured with an airborne Synthetic Aperture Radar (SAR). Directional spectra of gravity waves are obtained with the SAR both in open waters and below an ice cover. Further work is needed in order to verify SAR-measurements with in-situ observations. In-situ measured directional spectra are also compared with hindcast spectra from the 3G-WAM model. Hindcast significant wave heights were found to be lower than the in-situ measurements.The littoral drift model developed at DHI and ISVA, see Deigaard et al. (1986b) has been extended to include the effects of the irregularity of the waves, of a coastal current and a wind acting on the surf zone. Further, a mathematical model to simulate the near-shore current pattern along a barred coast with rip channels has been developed. The influence on the littoral drift of the irregularity of waves, wind, coastal current, and rip channels is discussed. It is concluded that irregularity of waves and presence of rip channels must be considered while coastal current and wind action are of minor importance.At present, the Prodhoe Bay oil field in Alaska contributes a substantial amount of the domestic oil production of the United States. Oil is also expected to be present on the continental shelf of Alaska, and it is estimated that approximatedly 28 percent of the total U. S. reserve is located beneath the shallow ice covered seas of the Alaskan continental shelf. To expolre and to exploit these oil rich resources, engineers are confronted with hostile oceanographic conditions such as high tides, waves, strong currents and sea ice. The same area is also rich in fishery resources. Being one of the most productive fishing grounds in the nothern Pacific, the potential ecological impact due to an oil spill is of a major concern. This paper describes the methologies used for the development of a modeling system for the oil risk analysis. The system is designed with generality in mind so it can be used for other coastal areas. The development of three dimensional models used in the modeling system described here have been published in the earlier International Coastal Engineering Conferences (Liu and Leendertse, 1982, 1984, 1986) and a report published recently by RAND (Liu and Leendertse, 1987). In the oil-spill risk analysis, these three dimensional hydrodynamic models are coupled to a two-dimensional stochastic weather model and an oil weathering model.The two projects (LUBIATOWO 79 and LUBIATOWO 86) were aimed at study pore pressure behaviour in natural sand bed in the coastal zone of the Baltic sea under the action of storm waves. During both projects, the wave induced pore pressures at the various levels in the sea bed were measured. The collected data were used to verify the applicability of the various theoretical approaches. In the conclusion, the range of the application of the particular analytical method is given.The rapid recession of the shingle bank of Hurst Beach (up to 3.5m/yr) makes it an excellent natural laboratory for the study of the factors which influence the stability of shingle beaches. Studies have included: the significance of long period, high energy, swell waves the classification and quantification of overwash processes run-up and seepage characteristics the effect of settlement of the underlying strata and the implications for practices in shingle nourishment. The studies have revealed the distinctive character of shingle beaches as compared with the more fully researched sand beaches. More detailed research on shingle beaches is justified particularly in relation to (i) the run-up characteristics including its interaction with swash cusps and (ii) the influence of the subsidiary sand fraction on the beach characteristics.Environmental assessment, engineering studies and designs were completed for a new 26.5 m3/s seawater intake system in the Persian Gulf. The original intake facility consisted of a curved, 60m breakwater with one end attached to the shoreline, a settling basin immediately adjacent to the shoreline and dredged to a maximum depth of approximately 5m, and a pumphouse structure located on shore such that the seaward wall formed one side of the settling basin. The facility located on an island in the Gulf, which served multiple seawater uses, had experienced both structural and operational problems, the latter consisting principally of excessive ingestion of sediment and seaweed. These factors plus the requirement for additional demands for seawater beyond plant capacity caused the owner to initiate a study of alternative intake systems, produce a design for the most effective solution and construct the new intake system.A two-dimensional wave prediction model suitable for use on personal computers is described. The model requires the twodimensional time-dependent wind field as input. Output consists of wave height, wave period, and wave direction estimates at all grid points on a computational grid representing an enclosed or semi-closed basin. Model predictions compare favorably with observations from a wave research tower in Lake Erie. A formula is provided to estimate how long a model simulation would take on a personal computer given the surface area of the computational domain, the grid size, and the computer clock speed.Cullera Bay is a neritic ecosystem placed on the Spanish Mediterranean Littoral largely influenced by the Jucar River, that brings about lower salinities than surrounding waters, and broad variations of its values. An extensive research, with 9 samplings throughout the year, was carried out, measuring both physical and chemical parameters, and the planktonic communities. The trophic status of the ecosystem, the spatial and temporal variations of the nutrients and the planktonic communities were studied, evaluating the influence of the river loads and the littoral dynamics. Some essential basis to allow a suitable emplacement of waste waters disposals along the Valencian littoral are set up in order to minimize the gradual eutrophication of this coast.In the last two years a whole of studies was realized in order to determine precise solutions to the regeneration of Villajoyosas beach, in the Spanish mediterranean coast. Investigations were carried out to the surrounding coastal areas based in field investigations and laboratory analyses of the beaches materials.

Deformation of Reef Breakwaters and Wave Transmission

The risk-based design of a reef breakwater requires the prediction of the temporal variations of the damage and wave transmission coefficient during storms. The cross-shore numerical model is extended to the landward zone of the wave transmission. The extended model is compared with 148 tests for a reef breakwater with a narrow crest at or above the still water level where the narrow crest was lowered by wave action.Themodelisalsocomparedwithanexperimentonawide-crestedsubmergedbreakwaterinwhichthecrestheightincreasedduring20-h wave action. The damage, crest height, and wave transmission coefficient are predicted reasonably well; however, the damaged profile is not

Wave Transformation and Runup on Dikes and Gentle Slopes

ABSTRACT Kobayashi, N.; Pietropaolo, J.A., and Melby, J.A., 2013. Wave transformation and runup on dikes and gentle slopes. Coastal flood-risk mapping requires the prediction of wave runup and overtopping of dikes and beaches. The cross-shore numerical model CSHORE is adjusted to predict irregular wave runup on impermeable dikes. The model is compared with 137 wave runup tests and 97 wave overtopping tests. The seaward boundary of the computation is taken at the location where wave setup is negligible. The spectral period and peak period at this boundary location are specified as input. The model predicts the measured cross-shore variation of the spectral significant wave height on the barred and sloping beaches in front of the dikes. The measured 2% and 1% exceedence runup heights are predicted within errors of about 20% for the spectral period used as input to CSHORE. The model predicts the threshold of wave overtopping, but the minor wave overtopping rates can be predicted only within a factor of 10. The model is also compared with 120 tests for wave runup on gentle uniform slopes as well as wave runup data on natural beaches in order to assess the utility of the numerical model for coastal flood-risk mapping on sand beaches.

THE CORE-LOC: OPTIMIZED CONCRETE ARMOR

A special reflecting wall 12 m long and 2.1 m high was built off the beach at Reggio Calabria, and 30 wave gauges were assembled before the wall and were connected to an electronic station on land. It was possible to observe the reflection of wind waves generated by a very stable wind over a fetch of 10 Km. The experiment aimed to verify the general closed solution for the wave group mechanics (Boccotti, 1988, 1989), for the special case of the wave reflection.Significant features on Wadden Sea wave climate are evaluated in respect of the state of the art. Main emphasis was laid on an analysis of the governing boundary conditions of local wave climate in island sheltered Wadden Sea areas with extensions being sufficient for local wind wave growth. Explanatory for significant wave heights a reliable parametrization of local wave climate has been evaluated by using generally available data of water level and wind measurements.

Vulnerability and Impacts on Human Development

The societal vulnerability of U.S. coasts to climate change is multifaceted, including vulnerabilities of economic sectors, cultural resources, and human well-being of a diverse concentration of people. In addition to the vulnerability and potential impacts of a changing climate on natural resources and threats to ecosystem services described in Chapter 3, homes and other human development in the coastal zone are also increasingly at risk. This expanded vulnerability has three dimensions: exposure, sensitivity, and resilience or adaptive capacity. The interactions of climate-related vulnerabilities with other stresses, such as economic downturn, environmental degradation, loss of ecosystem services, and continued pressures for development pose further analytical challenges. Current research on societal vulnerability in the coastal area does not yet fully consider or capture these multifaceted attributes of societal vulnerability.